The invention relates to apparatus for automatically depressurizing a variable-volume inflatable enclosure, such as a cuff.
In the past a number of inventors have sought to provide machines that automatically detect blood pressure and automatically indicate and/or record the detected measurements on an X-Y chart or the like in such manner that a physician or other trained observer can rapidly determine the systolic and diastolic pressures at a glance from the recording and can easily distinguish the valid pressure markings from artifacts.
Typically, the blood pressure measurements are taken with the aid of an inflatable cuff which has been applied to a patient and pressurized to a value initially higher than the patient's systolic pressure and which has thereafter been depressurized. The scan of the timing axis of the X-Y chart is syncchronized with the rate of depressurization of the cuff.
One problem with such arrangements is that the linearity of the depressurization, and thereafter the accuracy of the scan of the chart drive, has not been sufficiently precise to obtain an optimum display and/or record for the observer.